I'm trying to install some conversion tracking scripts on a few thank-you pages on my blog. I've tried inserting the script using the HTML editor and also by using the Website Optimizer Plugin hack -- no luck getting the page verified by Google.

Ok I got it to work without the optimizer plugin or creating templates.
I went into my footer.php file and put this in:
<?php
if (is_page('thanks-for-joining'))
{ include ("conversion_free.html"); }
elseif (is_page('thanks-for-joining-silver-level-membership'))
{ include ("conversion_silver.html"); }
?>

create an html text file for each conversion script (paste from google site) and give it a unique filename. save it where your themes are.
Add as many elseif's as you need. I used the permalink name of page, you can also use the page id as well.